Method of manufacturing composite insulator and packing member for use in same

ABSTRACT

In a method of producing a composite insulator having a core member, end fitting members fixed to both end portions of the core member, and an overcoat member including a sheath portion formed on an outer surface of the core member and shed members, the overcoat member and the end fitting member are connected by curing. Moreover, a clamping operation is performed or a packing member is used for preventing a flow of an overcoat forming material into a seal portion. In this manner, it is possible to improve a seal performance of a connection boundary between the end fitting member and the overcoat member.

TECHNICAL FIELD

[0001] The present invention relates to a method of producing acomposite insulator comprising a core member made of for example FRP,end fitting members fixed to both end portions of the core member, andan overcoat member made of insulation material having a sheath portionformed on an outer surface of the core member and shed portions, andalso relates to a packing member used for this composite insulatorproducing method which is arranged for preventing a flow of an overcoatforming material into a gap between the core member and the end fittingmember fixed to both end portions of the core member.

BACKGROUND ART

[0002] Up to the present, the composite insulator comprising the coremember, the end fitting members fixed to both end portions of the coremember, and the overcoat member having the sheath portion formed on thecore member and the shed portions is produced by various methods forexample by arranging the end fitting members on both end portions of thecore member, setting the core member and the end fitting members in ametal mold, filling the overcoat forming material in the metal mold, andcuring the overcoat forming material. Moreover, in order to improve aseal performance between the end fitting member and the overcoat formingmaterial, there is known a technique such that an overcoat formingmaterial of room temperature hardening type (RTV) is used as theovercoat forming material, and also there is known a technique such thata material such as silicone gel is arranged between the end fittingmember and the overcoat forming material.

[0003] Even in the method using the RTV or the method using silicone gelmentioned above, it is possible to maintain a normal seal performance,but recently more excellent seal performance is to be required.Therefore, particularly in the case of the composite insulator in whichthe overcoat member is made of an insulation material such as siliconerubber, there is a desire to obtain a method of producing a compositeinsulator in which a seal performance of a connection boundary betweenthe end fitting member and the overcoat forming material can bemaintained and an end portion of the core member can be firmly connectedto an inner surface of a core member insertion hole of the end fittingmember.

DISCLOSURE OF THE INVENTION

[0004] An object of the invention is to eliminate the drawbacksmentioned above and to provide a method of producing a compositeinsulator in which a seal performance of a connection boundary between aend fitting member and an overcoat member can be improved and a packingmember used for this producing method.

[0005] According to the invention, a method of producing a compositeinsulator having a core member, end fitting members fixed to both endportions of the core member, and an overcoat member including a sheathportion formed on an outer surface of the core member and shed members,is characterized in that the overcoat member and the end fitting memberare connected by curing.

[0006] According to the invention, a packing member used for the methodof producing a composite insulator having a core member, end fittingmembers fixed to both end portions of the core member, and an overcoatmember including a sheath portion formed on an outer surface of the coremember and shed members, and arranged for preventing a flow of theovercoat forming material into a gap between the core member and the endfitting member fixed to an end portion of the core member, ischaracterized in that, if the packing member is once positioned in theend fitting member, the packing member is not moved in a directionpulling up from a position at which the packing member is positioned,when the end portion of the core member is moved in a direction pullingup from the end fitting member.

[0007] In the method of producing a composite insulator according to theinvention, since a seal portion between the overcoat member and the endfitting member is constructed by curing, it is possible to improve aseal performance between the overcoat member and the end fitting member.Moreover, in the preferred embodiment, it is possible to provide a morefirm curing connection between the end fitting member and the overcoatmember by roughing an upper surface of the end fitting member or bysubjecting a phosphate treatment to a galvanization of a surface of theend fitting member.

[0008] In the preferred embodiment of the method of producing acomposite insulator according to the invention, the seal portion iscured for connection under a condition such that the end fitting memberis not clamped to the end portion of the core member. In addition, thecore member itself or an end portion of the core member and an innersurface of a core member insertion hole are finely worked so as toprevent a substantial flow of the overcoat forming material between anouter end surface of the core member and an inner surface of the coremember insertion hole of the end fitting member when the end portion ofthe core member is inserted into the core member insertion hole of theend fitting member, and thus the end fitting member is fixed to the coremember before forming operation or the end fitting member ispreliminarily fixed to the core member before forming operation. If theovercoat forming material is flowed between an end portion of the coremember and an inner surface of the core member insertion hole of the endfitting member, it is not possible to clear an specified tensilestrength due to an abrasion resistance between the core member and theend fitting member.

[0009] Moreover, in the preferred embodiment of the method of producinga composite insulator according to the invention, since the seal portiondefined by the overcoat member, the core member and the end fittingmember is integrally formed by arranging the end fitting members to theboth end portions of the core member without clamping, setting them inthe metal mold, filling the overcoat forming material into an overcoatforming space between an outer surface of the core member and the metalmold, and curing under pressure so as to form the overcoat member and toconnect the overcoat member to the end fitting member, or since theboundary between the end fitting member and the overcoat member issealed by mold-forming the overcoat member around the core member,arranging the end fitting members at both end portions of the coremember without clamping in such a manner that an end portion of the endfitting member is overlapped on an end portion of the overcoat member,arranging an insulation polymer material near the boundary exposedexternally between the end fitting member and the overcoat member, andheating the insulation polymer material so as to cure the insulationpolymer material, or since the boundary between the end fitting memberand the overcoat member is sealed by mold-forming the overcoat memberaround the core member, arranging the end fitting members at both endportions of the core member without clamping in such a manner that a gapis existent between an end portion of the end fitting member and an endportion of the overcoat member, arranging an insulation polymer materialin the gap between the end fitting member and the overcoat member, andheating the insulation polymer material so as to cure the insulationpolymer material, it is possible to improve the seal performance. Inaddition, since a clamping operation with respect to an end portion ofthe core member is performed only once, it is possible to reduce anamount of producing steps of the composite insulator.

[0010] Further, in the method of producing a composite insulatorcomprising a core member, end fitting member fixed to both end portionsof the core member, and an overcoat member having a sheath portionformed on an outer surface of the core member and shed portions, thepacking member according to the invention is provided for preventing aflow of an overcoat forming material into a gap between the core memberand the end fitting member fixed to an end of the core portion. If thepacking member is once positioned in the end fitting member, thispacking member is not moved in a direction pulling up from a position atwhich the packing member is positioned, when the end portion of the coremember is moved in a direction pulling up from the end fitting member.

[0011] Accordingly, in the case that the composite insulator istransferred after the end fitting member is inserted into an end portionof the core member and the packing member is positioned at apredetermined portion in the end fitting member, if an end portion ofthe core member is moved in a direction pulling up from the end fittingmember, the packing member is not moved in a direction pulling up fromthe position at which the packing member is preliminarily positioned inthe end fitting member and is maintained at a predetermined position inthe end fitting member.

[0012] Therefore, it is possible to stably seal a boundary between thecore member and the end fitting member and to prevent a flow of overcoatforming material into a boundary between the core member and an innersurface of the core member insertion hole of the end fitting member.Moreover, since a metal mold is preliminarily heated and shows a thermalexpansion due to a shortening of forming time and the core membermaintained at room temperature is arranged in the heated metal mold, theovercoat member is formed under such a condition that an end surface ofthe core member is inserted into the core member insertion hole of theend fitting member with a little gap between an end surface of the coremember and a bottom surface of the core member insertion hole or that anend surface of the core member is once connected to an bottom surface ofthe core member insertion hole and then the core member is slightlypulled up from the core member insertion hole so as to generate a littlegap between an end surface of the core member and a bottom surface ofthe core member insertion hole. Even in the latter case, if the endfitting member is inserted into an end portion of the core member andthe packing member is once positioned at a predetermined position in theend fitting member, the packing member is not moved in a directionpulling up from the position at which the packing member is oncepositioned and is maintained at a predetermined position in the endfitting member. Therefore, it is possible to stably seal a boundarybetween the core member and the end fitting member and to prevent a flowof overcoat forming material into a boundary between the core member andan inner surface of the core member insertion hole of the end fittingmember.

BRIEF DESCRIPTION OF DRAWINGS

[0013]FIG. 1 is a schematic view for explaining one embodiment of amethod of producing a composite insulator according to the invention,wherein

[0014]FIG. 1(a) is a cross sectional view showing a state such that theend fitting members are arranged to both end portions of the core memberand

[0015]FIG. 1(b) is a cross sectional view illustrating a state such thatthe core member to which the end fitting members are arranged is setbetween a pair of metal mold units and the core member is fastened bythe metal mold units;

[0016]FIG. 2(a) is a cross sectional view depicting a state such thatthe end fitting members are arranged to both end portions of the coremember and

[0017]FIG. 2(b) is a cross sectional view showing a state such that thecore member to which the end fitting members are arranged at the bothend portions is set between a pair of metal mold units and the coremember is fastened by the metal mold units;

[0018] FIGS. 3(a)-(c) are schematic views for explaining a method ofproducing a composite insulator according to the invention in which anovercoat forming material is filled in a overcoat forming space Sbetween an outer portion of the core member and the metal mold under thecondition such that a packing member 6 is provided for preventing a flowof overcoat forming material into a gap between the core member and theend fitting member arranged to an end portion of the core member, andthe overcoat forming material is cured under pressure;

[0019]FIG. 4 is a perspective view showing a packing member;

[0020]FIG. 5(a) is a perspective view illustrating another packingmember and

[0021]FIG. 5(b) is an enlarged cross sectional view of the anotherpacking member;

[0022]FIG. 6 is a cross sectional view depicting a state such that thepacking member shown in FIG. 5 is firmly connected to an end surface ofthe end fitting member and an outer surface of the core member near theend surface of the end fitting member;

[0023]FIG. 7 is a schematic view explaining one preferred embodiment ofa method of producing a composite insulator according to the invention;

[0024]FIG. 8 is a schematic view showing another method of producing acomposite insulator according to the invention in an order of producingsteps;

[0025]FIG. 9 is a schematic view illustrating one end portion of thecomposite insulator obtained according to the another method ofproducing a composite insulator according to the invention;

[0026]FIG. 10 is a schematic view depicting still another method ofproducing a composite insulator according to the invention in an orderof producing steps;

[0027]FIG. 11 is a schematic view showing a construction of one endportion of the composite insulator obtained according to the stillanother method of producing a composite insulator according to theinvention; and

[0028]FIG. 12 is a schematic view illustrating one embodiment of aforming method of a seal portion in the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0029]FIG. 1 is a schematic view for explaining one embodiment of amethod of producing a composite insulator according to the invention,wherein FIG. 1(a) is a cross sectional view showing a state such thatthe end fitting members are arranged to both end portions of the coremember and FIG. 1(b) is a cross sectional view illustrating a state suchthat the core member to which the end fitting members are arranged isset between a pair of metal mold units and the core member is fastenedby the metal mold units. Firstly, as shown in FIG. 1(a), end fittingmembers 12 are clamped and fixed to both end portions of an FRP core 11as a core member. Then, as shown in FIG. 1(b), the FRP core 11 to whichthe end fitting members 12 are clamped at both end portions is set in ametal mold 13. Under such a condition, an overcoat forming material suchas silicone rubber is filled in an overcoat forming space s defined onan outer surface of the FRP core 11 in the metal mold 13. After that,the thus filled overcoat forming material is cured by applying heat andpressure thereto, thereby connecting the overcoat forming material tothe metal mold 13 and the end fitting members 12. Moreover, as ananother embodiment, the end fitting members 12 are clamped for apreliminarily connection to the ends of the FRP core 11 in the stepshown in FIG. 1(a), and then a composite insulator is once formedaccording to the same method mentioned above. After that, the endfitting members 12 are clamped again to the ends of the FRP core 11 toobtain a finally formed composite insulator.

[0030] In the both embodiments mentioned above, the step of connectingor preliminarily connecting the end fitting members 12 to the ends ofthe FRP core 11 is for preventing an insertion of the overcoat formingmaterial into a boundary between the end fitting member 12 and the FRPcore 11. Moreover, in the both embodiments mentioned above, it is afeature of the invention that the overcoat forming material is cured forconnection to the end fitting member 12. In the present invention, aphrase “the overcoat forming material is cured for connection to the endfitting member 12” means that a seal portion between the overcoat memberand the end fitting member 12 is chemically reacted to obtain a firmconnection by the same reaction as the curing reaction in the overcoatmember forming step. It is preferred to perform the step of curing theovercoat forming material to the end fitting member 12 at the same timeas that the forming step such that the sheath portion and the shedportions are cured under pressure.

[0031] In the embodiments mentioned above, it is preferred to rough asurface of the end fitting member 12 to which the overcoat formingmaterial is contacted when the overcoat forming material is cured forconnection to the end fitting member 12. If the surface of the endfitting member 12 is roughed, an oil component for example adhered tothe surface can be removed and a surface area used for connection can beincreased, so that it is possible to perform a stable curing operation.A portion 95% or more of the cured portion can be used for a connectionin the case of the roughed surface, but a portion only 20-80% of thecured portion can be used for a connection in the case of the normalsurface. Moreover, if a phosphate treatment is performed with respect toa surface of the end fitting member 12 to which the overcoat formingmaterial is contacted i.e. a surface on which a normal galvanization isperformed, a surface area is increased due to a growth of an acicularcrystalline of zinc phosphate, and the surface is stabilized and is easyto be connected. Therefore, this is a preferred embodiment.

[0032] In the present invention, as an overcoat forming method,compression forming method, injection forming method, and transferforming method can be used. In this specification, an explanation ismade for the composite insulator having a solid core member, but thepresent invention can be applied for a composite hollow insulator havinga cylindrical core member. Here, differences on rubber material, formingcondition etc. between the composite insulator and the composite hollowinsulator are shown in the following Table 1. As shown in Table 1,rubber material and forming condition such as forming pressure andforming temperature are different between the composite insulator andthe composite hollow insulator due to whether the core member is solidor cylindrical. Therefore, it is not always possible to apply theforming condition of the composite hollow insulator to the compositeinsulator as it is. TABLE 1 Differences on rubber material or formingcondition between hollow insulator and suspension insulator Item Hollowinsulator Suspension insulator Rubber state Liquid Solid Curing reactioncatalyst Platinum Organic peroxide Forming stress 10˜20 kgf/cm²  80˜200kgf/cm² Forming temperature 20˜80° C. 150˜200° C.

[0033] In the embodiment mentioned above, when the step of curing theend fitting member and the overcoat member is performed, the end fittingmember is connected or preliminarily connected to the FRP core. Thepresent inventors further investigated the embodiment mentioned above,and found the following evidences. That is to say, in the embodimentmentioned above, the overcoat member is formed by arranging the overcoatforming material on an outer portion of the core member after the endfitting member is clamped to the core member for the purpose ofpreventing a flow of the overcoat forming material. This is because itis not possible to clear a specified tensile strength due to an abrasionresistance between the core member and the end fitting member, if theovercoat forming material is inserted between the end portion of thecore member and the inner surface of the core member insertion hole ofthe end fitting member.

[0034] However, the present inventors further investigated in detail theseal performance and the connection condition between the end portion ofthe core member and the inner surface of the core member insertion holeof the end fitting member, and found the following results. That is tosay, in the embodiment mentioned above, a compression stress due to aclamping operation, within a limit such that a crack is not generated inthe core member, is applied to the core member. However, since a heatover a glass transition point is applied to the core member during theovercoat member forming step, the core member is shrunk on its diameterand thus there is a possibility such that a tensile strength of thecomposite insulator is decreased.

[0035] Further investigation was conducted on the basis of the resultsmentioned above and the following preferred embodiments were found.

[0036] (1) The overcoat forming material is filled in the overcoatforming space between the outer portion of the core member and the metalmold under the condition such that the packing member for preventing aflow of the overcoat forming material into a gap between the core memberand the end fitting member connected to the end of the core member isprovided, and is cured under pressure. In this case, it is possible tostably seal a connection portion between the core member and the endfitting member and to prevent a flow of the overcoat forming materialinto a gap in the connection portion between the core member and theinner surface of the core member insertion hole. In addition, the innerend portion and the outer end portion of the packing member is firmlycontacted to an end portion outer surface of the core member and theinner surface of the core member insertion hole of the end fittingmember respectively.

[0037] (2) The packing member is made of a material which does notprevent a connection performance with the overcoat forming material or amaterial which does not affect the curing operation. In this case, adesired connection by curing under pressure between the overcoat memberand the core member or between the end fitting member and the overcoatmember is not prevented even if the packing member is provided. Forexample, this chan be accomplished by using the same curing agent forthose of the overcoat forming material and the packing member.

[0038] (3) The inner portion of the end fitting member has a shape suchthat the packing member can be set in the end fitting member by slidingit. Therefore, even when the packing member is positioned at near butcorrect position in the end fitting member, the packing member can beslid and positioned in the end fitting member by means of a filledovercoat forming material in the case of filling the overcoat formingmaterial in the overcoat forming space between the metal mold and theouter portion of the core member. Moreover, it is not necessary toposition the packing member in the inner portion of the end fitting moldstrictly before performing the overcoat member forming, and thus it ispossible to perform this step easily.

[0039] (4) In the case that the packing member is once positioned in theend fitting member, the packing member is not moved in a directionpulling up from the position at which it is positioned in the endfitting member, even if the end portion of the core member is moved in adirection pulling up from the end fitting member. Even in the case thatthe overcoat member is formed under such a condition that the endsurface of the core member is once contacted to the bottom surface ofthe insertion hole of the end fitting member and then the core member ispulled up slightly from the end fitting member to form a little gapbetween the end surface of the core member and the bottom surface of theinsertion hole of the end fitting member, with taking into considerationof the case such that the core member before expansion is arranged in apreviously heated and expanded metal mold, the packing member is stoppedat a predetermined position in the end fitting member without moving ina direction pulling up from a position at which the packing member ispositioned with respect to the end fitting member. Therefore, it ispossible to stably seal the boundary between the core member and the endfitting member and to prevent the flow of the overcoat forming materialinto a gap between the core member and the inner surface of the coremember insertion hole of the end fitting member.

[0040] (5) The packing member is a packing having a V-shape crosssection. In this case, both open end portions having a V-shape i.e. aninner end portion and an outer end portion are firmly contacted to anouter surface of the end portion of the core member and an inner surfaceof the core member insertion hole of the end fitting memberrespectively, and a valley portion positioned at an intermediate portionof the both end portions having a V-shape is positioned at a side of thebottom portion of the core member insertion hole of the end fittingmember as compared wit the both open end portions. In this case, theposition of the valley portion is not limited to the just intermediateportion of the both open end portions having a V-shape, and can bedeviated toward either sides of the open end portions i.e. an inner sideor an outer side in a diameter direction of the open end portions.Moreover, the packing member may have a V-shape cross section to whichthe end surface of the end fitting member and the surface of the coremember near the above end surface are closely contacted. In this case,if the overcoat forming material is filled in the overcoat forming spaceunder such a condition that the packing member is set at an outersurface of the core member, the packing member is closely contacted tothe end surface of the end fitting member and the surface of the coremember near the end surface mentioned above without being bent by theovercoat forming material filling stress. Therefore, it is possible toprevent the flow of the overcoat forming material into the gap betweenthe end fitting member and the core member.

[0041] Hereinafter, preferred embodiments mentioned above will beexplained with reference to the drawings. FIG. 2(a) is a cross sectionalview showing a state such that the end fitting members are arranged onthe both end portions of the core member, and FIG. 2(b) is a crosssectional view illustrating a state such that the core member to whichthe end fitting members are arranged at the both end portions is setbetween a pair of metal mold units and the core member is fastened bythe metal mold units. In the figure, end fitting members 2 a, 2 b arearranged respectively to both end portions 1 a, 1 b of a core member 1without clamping. Core member insertion holes 3 a, 3 b are formed in theend fitting members 2 a, 2 b respectively, and respective core memberinsertion holes 3 a, 3 b have a two step hole construction comprisingfirst small diameter hole portions 3 a-1, 3 b-1 positioned at an outerside in an axial direction and second large diameter hole portions 3a-2, 3 b-2 positioned at an inner side in an axial direction. Diametersof the first small diameter hole portions 3 a-1, 3 b-1 are worked insuch a manner that the column shaped core member is inserted withsubstantially no gap into inner surfaces of the small diameter holeportions. Diameters of the second large diameter hole portions 3 a-2, 3b-2 positioned at the inner side in the axial direction are larger thanan outer diameter of the core member and thus a part of the overcoatmember is existent in a gap defined by an outer surface of the coremember and an inner surface of the large diameter hole portion. In thismanner, a seal length between the end fitting member and the overcoatmember is increased, and thus it is possible to improve a sealperformance. Cylindrical expanding portions 4 a, 4 b positioned at anouter side in a radial direction are arranged at cylindrical open endportions of the large diameter hole portions 3 a-2, 3 b-2 of the endfitting members, and a seal length between the end fitting member andthe overcoat member is further increased in the same manner as that ofthe large diameter hole portion, so that a seal performance is furtherimproved.

[0042]FIG. 2(b) is a cross sectional view illustrating a state such thatthe core member 1 to which the end fitting members 2 a, 2 b are arrangedat the both end portions 1 a, 1 b is set between a pair of metal moldunits 5 a, 5 b and the core member is fastened by the metal mold units.An overcoat forming space S is formed between a pair of the metal moldunits 5 a, 5 b. The overcoat forming space S comprises a sheath formingportion S1 and shed forming portions S2. Close contacts are accomplishedbetween outer surfaces of open cylindrical end portions of the largediameter hole portions 3 a-2, 3 b-2 of the end fitting members and theopposed metal mold units and between the core member and inner surfacesof the core member insertion holes of the end fitting members, and thusan outer side and an inner side seals in a radial direction areachieved. The cylindrical expanding portions 4 a, 4 b positioned at anouter side in a radial direction are closely contacted to end portionsof the overcoat forming space S of the metal mold units. An overcoatforming material is supplied in the overcoat forming space S from anovercoat forming material feeding path not shown, and an overcoat memberis formed on an outer surface of the core member in the overcoat formingspace S by heating the overcoat forming material under pressure, so thatthe overcoat member is connected to the opposed surface of the endfitting member. If necessary, a primer is preliminarily sprayed onsurfaces of the end fitting member and the core member to which theovercoat member is contacted, and thus the overcoat member is connectedto an outer surface of the core member and the opposed surface of theend fitting member via a primer. After that, a pair of the metal moldunits 5 a, 5 b are opened to pull up a formed composite insulator body,and the end fitting members are clamped at the both end portions of thecore member under a predetermined clamping stress.

[0043] FIGS. 3(a)-(c) are schematic views for explaining a method ofproducing a composite insulator according to the invention in which theovercoat forming material is filled in the overcoat forming space Sbetween an outer portion of the core member and the metal mold under thecondition such that a packing member 6 is provided for preventing a flowof the overcoat forming material into a gap between the core member 1and the end fitting member 3 a (same as end fitting member 3 b) arrangedto an end portion of the core member, and the overcoat forming materialis cured under pressure. In this embodiment, an inner shape of the largediameter hole portion 3 a-2 of the core member insertion hole 3 a in theend fitting member 2 permits a sliding of the packing member 6 so as toset the packing member 6. In FIGS. 3(a)-(c), the packing member 6 has aV-shape cross section (refer to FIG. 4), and the both open end portionsi.e. an inner end portion 6-1 and an outer end portion 6-2 are firmlycontacted to an outer surface of the end portion of the core member 1and an inner surface of the large diameter hole portion 3 a-2 of the endfitting member 2 respectively. In addition, the valley portion 6-3positioned at an intermediate portion of the both open end portionshaving a V-shape is positioned at a bottom side of the core memberinsertion hole (small diameter hole portion) as compared with the bothopen end portions. In this case, the valley portion is positioned atjust intermediate portion of the both open end portions having aV-shape.

[0044]FIG. 3(a) shows an intermediate step for positioning the packingmember at a predetermined position on the bottom portion of the largediameter hole portion 3 a-2 of the end fitting member 2 a shown in FIG.3(b). The core member 1 shown in the state illustrated in FIG. 3(b), inwhich the end fitting members 2 a, 2 b are arranged to the both endportions 1 a, 1 b, is set between a pair of the metal mold units 5 a, 5b, and the metal mold units 5 a, 5 b are closed. After that, theovercoat member is formed in the same manner as explained in FIG. 2(b),and then the end fitting members may be clamped to the core member ifnecessary. Otherwise, the core member 1 maintained in the state shown inFIG. 3(a), in which the end fitting members 2 a, 2 b are arranged to theboth end portions 1 a, 1 b, is set between a pair of the metal moldunits 5 a, 5 b, and the metal mold units 5 a, 5 b are closed. Afterthat, the overcoat member is formed in the same manner as explained inFIG. 2(b), and then the end fitting members are clamped to the coremember. In this case, the packing member is deformed externally in anaxial direction by the overcoat forming material supplied in theovercoat forming space S, and is positioned as shown in FIG. 3(b).

[0045]FIG. 3(c) is a schematic view explaining the state such that thepacking member is not moved in a direction pulling up from the positionat which it is set in the end fitting member even if the end portion ofthe core member is moved in a direction pulling up from the end fittingmember. That is to say, even in the case that the overcoat member isformed under such a condition that the end surface of the core member isonce contacted to the bottom surface of the insertion hole of the endfitting member and then the core member is pulled up slightly from theend fitting member to form a little gap between the end surface of thecore member and the bottom surface of the insertion hole of the endfitting member, with taking into consideration of the case such that thecore member maintained at room temperature is arranged in a previouslyheated and expanded metal mold, the packing member is stopped at apredetermined position in the end fitting member without moving in adirection pulling up from a position at which the packing member ispositioned with respect to the end fitting member. Therefore, it ispossible to stably seal the boundary between the core member and the endfitting member and to prevent the flow of the overcoat forming materialinto a gap between the core member and the inner surface of the coremember insertion hole of the end fitting member.

[0046]FIG. 5(a) and FIG. 5(b) are a perspective view and an enlargedcross sectional view respectively showing another embodiment of thepacking member shown in FIGS. 3(a)-(c). FIG. 6 is a cross sectional viewshowing the state such that a packing member 6′ is closely contacted tothe inner side in a radial direction of the core member insertion hole 3a i.e. the end surface of the large diameter hole portion 3 a-2 and theouter surface of the core member near the end surface mentioned above.The packing member 6′ has little different construction and function asthose of the packing member 6, but has a substantially same function asthat of the packing member 6 shown in FIGS. 3(a)-(c). Therefore, thesame explanations conducted for the packing member 6 may be applied tothe packing member 6′. Hereinafter, different points will be explainedmainly.

[0047] The packing member 6′ has the similar shape as that of thepacking member 6 and has a cross sectional shape shown in FIG. 5(b).More detail explanation is as follows. The packing member 6′ comprises asmall diameter end portion 6′-1 which is contacted to the outer surfaceof the core member under expanded state, a large diameter end portion6′-2 which is contacted to the inner side in an axial direction of thecore member insertion hole 3 a provided in the end fitting member undershrunk state i.e. the inner surface of the second large diameter holeportion 3 a-2, and a connection end portion 6′-3 connected between thesmall diameter end portion 6′-1 and the large diameter end portion 6′-2and positioned at the outer side in an axial direction when the packingmember is set between the core member and the end fitting member. Inaddition, a cylindrical depression portion 6′-4 serving as an easybending in a radial direction of the small diameter end portion 6′-1 andthe large diameter end portion 6′-2 is provided at the inner side in anaxial direction between the small diameter end portion 6′-1 and thelarge diameter end portion 6′-2. In FIG. 5(a) and FIG. 5(b), no load isapplied to the packing member 6′, and a broken line (1) and a brokenline (2) show respectively a fictitious inner surface of the largediameter hole portion 3 a-2 provided at the inner side in an axialdirection of the core member insertion hole 3 a and a fictitious outersurface of the core member. A first surface 6′-3 a of the connection endportion 6′-3 opposed to the core member is extended substantiallyparallel to the outer surface of the core member. Moreover, a secondsurface 6′-3 b opposed to an inner end surface of the second largediameter hole portion 3 a-2 provided at an inner side in an axialdirection of the core member insertion hole 3 a of the end fittingmember is extended substantially parallel to the inner end surface ofthe second large diameter hole portion 3 a-2.

[0048] The overcoat forming material is filled in the overcoat formingspace after the packing member 6′ is arranged to the outer surface ofthe core member and is positioned in the second large diameter holeportion 3 a-2 provided at the inner side in an axial direction of thecore member insertion hole 3 a of the end fitting member and the metalmold units are closed. In this case, the packing member 6′ can be firmlyfitted to the end surface of the second large diameter hole portion 3a-2 provided at the inner side in an axial direction of the core memberand the outer surface of the core member near the end surface mentionedabove. Therefore, it is possible to effectively prevent a flow of theovercoat forming material into the gap between the outer surface of thecore member and the end fitting member. Moreover, when the packingmember 6′ is pressed toward the metal member 3 a by a forming stress andis deformed, the first surface 6′-3 a is firmly contacted to the coremember, and the second surface 6′-3 b is fly contacted to the connectionsurfaces of the metal member inner surfaces 3 a-1, 3 a-2. Therefore, itis possible to prevent a flow of the overcoat forming material into thegap between the outer surface of the core member and the end fittingmember.

[0049] Then, as a further preferred embodiment according to a method ofproducing a composite insulator according to the invention, an examplesuch that the overcoat member is formed by a compression forming and theend fitting member is introduced into a predetermined position in themetal mold by using a guide provided in the metal mold will beexplained. FIG. 7 is a schematic view explaining the preferredembodiment in the method of producing a composite insulator according tothe invention, wherein FIG. 7(a) shows a side view and FIG. 7(b)illustrates a front view. In the embodiment shown in FIGS. 7(a) and (b),an upper metal mold 31 and a lower metal mold 32 are respectivelyconstructed by integrating a plurality of segments.

[0050] Both of the upper metal mold 31 and the lower metal mold 32 havea cavity 35 for setting end fitting members 42 provided at the both endportions of an FRP core 41. Moreover, in the upper metal mold 32, aguide is constructed in such a manner that a pair of guide bars 36-1,36-2 having a space with each other whose distance is substantially same(little larger) as (than) a diameter of the end fitting member 42 arearranged upwardly at end portions corresponding to the end fittingmembers 42 respectively. Further, cavities 37-1, 37-2, in which theguide bars 36-1, 36-2 are settable when the upper metal mold 31 and thelower metal mold 32 are closed, are arranged at portions of the uppermetal member 32 corresponding thereto.

[0051] A method of forming the overcoat member by a compression formingby means of the upper metal mold 31 and the lower metal mold 32mentioned above is as follows. At first, a forming rubber 43 is woundand set on an outer surface of the FRP core 41 in which the end fittingmembers 42 are inserted into its end portions without clamping. Then,the FRP core 41, in which the forming rubber 43 and the end fittingmembers 42 are set, is set at a predetermined position on the lowermetal mold 32 i.e. the end fitting members 42 are set between the guidebars 36-1, 36-2 and the end fitting members 42 are positioned atportions corresponding to the cavity 35. After the settings mentionedabove, if a stress is applied under heating condition to the upper metalmold 31 and the lower metal mold 32 so as to close them, a desiredcomposite insulator can be formed by a compression forming.

[0052] Then, another embodiment of a method of producing a compositeinsulator according to the invention will be explained. FIGS. 8(a)-(d)are schematic views showing successive steps of the another embodimentof the method of producing the composite insulator according to theinvention in order. A construction of a polymer insulator as one exampleof the composite insulator according to the invention is the same asthat of the known polymer insulator. In this embodiment, as shown inFIG. 8(a), a layer 57 made of an overcoat forming insulation polymermaterial, here silicone rubber, for forming an overcoat member 56comprising a sheath portion 53 and shed portions 54 is formed around anFRP core 52. Then, as shown in FIG. 8(b), the overcoat member 56comprising the sheath portion 53 and shed portions 54 is formed byperforming a mold operation using the metal mold not shown. Then, asshown in FIG. 8(c), end fitting members 55-1, 55-2 are inserted intoboth end portions of the FRP core 52. Respective steps explained up tohere are the same as those of the known one.

[0053] Features of the another embodiment according to the inventionmentioned above are as follows. As shown in FIG. 8(d), when the endfitting members 55-1, 55-2 are arranged to both ends of the FRP core 52,the end portions of the end fitting members 55-1, 55-2 are overlapped onthe end portion of the overcoat member 56, and a silicone rubber member62 made of preferably the same material as that of the overcoat member56 is arranged on a boundary 61 exposed to the external atmospherebetween the end fitting members 55-1, 55-2 and the overcoat member 56 insuch a manner that the silicone rubber member 62 coverscircumferentially all of the boundary 56. Then, the thus obtained bodyis heated so as to cure the silicone rubber member 62, so that theboundary 61 between the end fitting members 55-1, 55-2 and the overcoatmember 56 is sealed. After that, the end fitting members 55-1, 55-2 areclamped. In this manner, as shown in FIG. 9 as one end portion, it ispossible to obtain the polymer insulator 51 having a seal portion 63made of a cured connection portion showing an excellent seal performancebetween the end fitting members 55-1, 55-2 and the overcoat member 56.In the polymer insulator 51 according to the invention produced in themanner shown in FIG. 8, since the cured connection portion showing anexcellent seal performance is existent on the boundary 61 between theend fitting members 55-1, 55-2 and the overcoat member 56, a sealperformance of the polymer insulator 51 as a whole can be improved.

[0054] In the another embodiment according to the invention, when theseal portion 63 is cured, the end fitting members 55-1, 55-2 are notclamped to the FRP core 52. Therefore, non-cured rubber used for acuring connection may be intruded between the inner surfaces of the endfitting members 55-1, 55-2 and the end portion of the sheath portion 53.In order to prevent such a non-cured rubber intrusion, prior to form theseal portion 63 by curing, it is preferred to firmly contact the innersurfaces of the end fitting members 55-1, 55-2 with respect to the endportion of the sheath portion 53.

[0055] FIGS. 10(a)-(d) are schematic views showing successive steps ofstill another embodiment of the method of producing the compositeinsulator according to the invention in order. In this embodiment,respective steps shown in FIGS. 10(a)-(c) are same as those of theembodiments shown in FIGS. 8(a)-(c). In this embodiment, differentpoints from the embodiment shown in FIG. 8 are as follows. The endfitting members 55-1, 55-2 are arranged at the both ends of the FRP core52 in such a manner that a gap 71 is existent between the end portionsof the end fitting members 55-1, 55-2 and the end portion of theovercoat member 56, and a silicone rubber member 72 made of preferablythe same material as that of the overcoat member 56 is arranged in thegap 71 between the end portions of the end fitting members 55-1, 55-2and the end portion of the overcoat member 56. Then, the thus obtainedbody is heated so as to cure the silicone rubber member 72, so thatportions between the end fitting members 55-1, 55-2 and the overcoatmember 56 are sealed by the seal portion 73. In this manner, the polymerinsulator 51 whose one end portion is shown in FIG. 11 can be obtained.Also in this embodiment, since the seal portion made of a curedconnection portion showing an excellent seal performance is existentbetween the end portions of the end fitting members 55-1, 55-2 and theend portion of the overcoat member 56, a seal performance of the polymerinsulator 51 as a whole can be improved.

[0056] In the still another embodiment according to the inventionmentioned above, when the seal portion made of the silicone rubbermember 72 is cured, the end fitting members 55-1, 55-2 are not clampedto the FRP core 52. Therefore, non-cured silicone rubber member 72 maybe intruded between the inner surfaces of the end fitting members 55-1,55-2 and the end portion of the sheath portion 53. In order to preventsuch a non-cured rubber intrusion, in the still another embodimentaccording to the invention mentioned above, it is preferred that use ismade of the packing member 6 as shown in the previous embodimentsmentioned above and the packing member 6 is arranged on surfaces of theend portions of the end fitting members 55-1, 55-2 which are contactedto the silicone rubber member 72.

[0057] The polymer insulators 51 according to the another embodiment andthe still another embodiment mentioned above have an advantage such thatit is previously formed since only the overcoat member 56 can bepreviously molded to the FRP core 52 in addition to the above mentionedimprovement of the seal performance. Moreover, it can deal with analternation of the shape of the end fitting member preferably. Further,in the embodiment mentioned above, an explanation is made to the exampleof the compression forming such that the overcoat forming material isarranged on the FRP core 52 and is molded by the metal mold, but thepresent invention can be used for the other forming methods such as theinjection forming such that the overcoat forming material is injected inthe metal mold in which the FRP core 52 is set. Furthermore, as amaterial of the seal portion which is cured later, the present inventioncan be achieved even if the other material as that of the overcoatmember 6 is used.

[0058]FIG. 12 is a schematic view showing a state such that the boundary61 between the end fitting members 55-1, 55-2 and the overcoat member 56is sealed in the another embodiment according to the invention. In thisembodiment, a pair of an upper metal mold 82 and a lower metal mold 83are set in such a manner that a cavity 81 is formed near the boundary 61between the end fitting members 55-1, 55-2 and the overcoat member 56.Then, silicone rubber is supplied into the cavity 81 through a supplyinlet 84. After that, the upper and lower metal molds are heated to forma seal portion near the boundary 61 between the end fitting members55-1, 55-2 and the overcoat member 56. Also in the still anotherembodiment according to the invention, it is possible to form the sealportion in the substantially same manner as that of the anotherembodiment mentioned above.

[0059] Industrial Applicability

[0060] As clearly understood from the above explanations, according tothe method of producing the composite insulator of the presentinvention, since the seal portion between the overcoat member and theend fitting member is cured for connection, it is possible to improvethe seal performance between the overcoat member and the end fittingmember. Moreover, according to the packing member of the presentinvention, since a construction of the packing member is specified, itis possible to firmly seal a portion between the core member and the endfitting member and to prevent a flow of the overcoat forming materialinto a portion between the core member and the inner surface of the coremember insertion hole of the end fitting member.

1. A method of producing a composite insulator having a core member, endfitting members fixed to both end portions of the core member, and anovercoat member including a sheath portion formed on an outer surface ofthe core member and shed members, characterized in that the overcoatmember and the end fitting member are connected by curing.
 2. The methodaccording to claim 1, wherein a surface of the end fitting member isroughed when the curing is performed.
 3. The method according to claim1, wherein a surface of the end fitting member is subjected to aphosphate treatment when the curing is performed.
 4. The methodaccording to one of claims 1-3, wherein a primer is applied to the endfitting member when the curing is performed.
 5. The method according toone of claims 1-4, wherein the core member and the end fitting memberare set in the metal mold and the overcoat member is heated for curingso that the core member and the overcoat member are connected and thesecuring member and the core member is also connected at the same time.6. The method according to claim 5, wherein the core member to which theend fitting members are clamped for connection is set in the metal mold,the overcoat forming material is filled in the overcoat forming space inthe metal mold provided on the outer portion of the core member, and thethus filled overcoat forming material is cured under pressure to formthe overcoat member.
 7. The method according to claim 5, wherein thecore member to which the end fitting members are clamped forpreliminarily connection is set in the metal mold, the overcoat formingmaterial is filled in the overcoat forming space in the metal moldprovided on the outer portion of the core member, the thus filledovercoat forming material is cured under pressure to form the overcoatmember, and the end fitting members are further clamed to both endportions of the core member.
 8. The method according to claim 5, whereinthe core member to which the end fitting members are arranged withoutclamping is set in the metal mold, the overcoat forming material isfilled in the overcoat forming space in the metal mold provided on theouter portion of the core member, the thus filled overcoat formingmaterial is cured under pressure to form the overcoat member, and theend fitting members are clamed to both end portions of the core member.9. The method according to one of claims 5-8, wherein the overcoatmember is formed by a compression forming.
 10. The method according toclaim 9, wherein the end fitting member is introduced into apredetermined position in the metal mold by using a guide provided inthe metal mold when the overcoat member is formed by a compressionforming.
 11. The method according to claim one of claims 8-10, whereinthe overcoat forming material is filled into the overcoat forming spacein the metal mold provided on the outer portion of the core member andis cured under such a state that a packing member for preventing a flowof the overcoat forming material into a gap between the core member andthe end fitting members connected to the end portions of the core memberis provided.
 12. The method according to claim 11, wherein the packingmember is formed by a material which does not affect a connectionperformance with the overcoat forming material and a curing performance.13. The method according to claim 11 or 12, wherein an inner shape ofthe end fitting member permits a sliding of the packing member.
 14. Themethod according to one of claims 11-13, wherein, in the case that thepacking member is once set in the end fitting member, if the end portionof the core member is moved in a direction pulling up from the endfitting member, the packing member is not mover in a direction pullingup from the position set in the end fitting member.
 15. The methodaccording to one of claims 11-14, wherein the packing member has aV-shaped cross section.
 16. The method according to claim 15, whereinthe packing member has a V-shaped cross section which can be closelycontacted to the end surface of the end fitting member and the outersurface of the core member near the end portion.
 17. The methodaccording to claim 1, wherein the overcoat member is molded around thecore member, the end fitting members are arranged to both ends of thecore member without clamping in such a manner that the end portion ofthe end fitting member is overlapped on the end portion of the overcoatmember, an insulation polymer material is arranged near a boundaryexposed to an external atmosphere between the end fitting member and theovercoat member and is cured to seal the boundary between the endfitting member and the overcoat member, and then the end fitting memberis clamped to the core member.
 18. The method according to claim 1,wherein the overcoat member is molded around the core member, the endfitting members are arranged to both ends of the core member withoutclamping in such a manner that a gap is existent between the end portionof the end fitting member and the end portion of the overcoat member, aninsulation polymer material is arranged near a boundary exposed to anexternal atmosphere between the end fitting member and the overcoatmember and is cured to seal the boundary between the end fitting memberand the overcoat member, and then the end fitting member is clamped tothe core member.
 19. The method according to claim 17 or 18, wherein theinsulation polymer material is the same as that of the overcoat formingmaterial which forms the overcoat member.
 20. The method according toone of claims 17-19, wherein the insulation polymer material is formedby using another metal mold as that used for forming the overcoatmember.
 21. A packing member used for the method of producing acomposite insulator having a core member, end fitting members fixed toboth end portions of the core member, and an overcoat member including asheath portion formed on an outer surface of the core member and shedmembers, and arranged for preventing a flow of the overcoat formingmaterial into a gap between the core member and the end fitting memberfixed to an end portion of the core member, characterized in that, ifthe packing member is once positioned in the end fitting member, thepacking member is not moved in a direction pulling up from a position atwhich the packing member is positioned, when the end portion of the coremember is moved in a direction pulling up from the end fitting member.22. The packing member according to claim 21, wherein the packing memberhas a V-shaped cross section.
 23. The packing member according to claim22, wherein the packing member has a V-shaped cross section which isclosely contacted to the end surface of the end fitting member and theouter surface of the core member near the end portion.